A vehicle outfitted with massive amounts of audio gear, with a large emphasis on the sub-stage. Usually running many thousands of watts on multiple large subwoofers. These cars are usually walled off and tuned really low.
Most are capable of hitting more than 155dB and have large battery banks and multiple high-output alternators so they can maintain that level all day long. These rides are usually capable of moving tons of air and can preform hairtricks and floating objects in the windows while slowly tearing the bodywork to shreds. They are equally impressive to look at as they are to hear.
"Did you make it to the show last weekend?"
"Hell yeah, there were at least a dozen guys that brought their Ground Pounders out. I got dozens of demos and a couple hours of awesome footage."